Infrared Variation of Radio-selected BL Lacertae Objects

In this paper, the historical infrared (JHK) data compiled from the published literature are presented in electronic form for 40 radio-selected BL Lacertae objects (RBLs) for the first time. Large variations are found and compared with the largest optical variations. Relations between color index and magnitude and between color-color indices are discussed individually. For the color-magnitude relation, some objects (0048-097, 0735+178, 0851+202, 1215+303, 1219+285, 1749+096, and perhaps 0219+428, 0537-441, and 1514-241) show that color index increases with magnitude, indicating that the spectrum flattens when the source brightens, while some other objects (0754+100, 1147+245, 1418+546, and 1727+502) perhaps show an opposite behavior, while the remaining objects do not show any clear tendency. For the color-color relation, it is found to be common that (J-K) is closely correlated with (J-H) while (J-H) is not correlated with (H-K).